1. Field of the Invention
The present invention relates to a freewheel hub for a bicycle, and more particularly a freewheel hub for a bicycle with even distribution of input torque and reliable transition between driving and non-driving modes of the freewheel.
2. Description of Related Art
Bicycles are fitted with a freewheel sprocket (70) on a hub (72) of a rear wheel (73), whereby when a transmission chain (74) drives the sprocket (70) clockwise, as seen in FIGS. 6 and 7, the entire rear wheel (73) is turned clockwise. When the bicycle is ridden, the rear wheel (73) is driven by the transmission chain (74), which in turn has been driven by a rider rotating a crank set (76). A rider may often wish to continue in motion on the bicycle without pedaling, such as going downhill. At such a time, the engagement between the sprocket freewheel (70) and the rear wheel hub (72) is released so that the chain (74) and the crank set (76) do not have to move in respect to the rotation of the rear wheel (73). As seen in FIG. 7, a prior art driving engagement between the freewheel sprocket (70) and the rear wheel hub (72) is via two pins (702) received in respective seats (705) and fitted between a core (704) and a collar (706) of the freewheel (70). The collar (706) has a ratchet bore comprising a plurality of alternating inclined faces (707) and shoulders (708). The pins (702) are urged away from their seats (705) by a respective one of two springs (709), whereby the pins (702) abut respective shoulders (708) in the core (704) and thus the entire freewheel sprocket (70) rotates. A bore defined through the core (704) has a threaded interior which threadingly engages with a male thread (not shown) formed on one side of the wheel hub, and thus when the core (704) turns, the rear wheel (73) turns to and vice-versa. However, when the rear wheel turns (73) but the rider does not turn the crank set, the rotating pins (702) slide over the inclined faces (707) of the ratchet bore and are pushed towards their seats (705) as the tension of the springs (709) is overcome. However, the freewheel sprocket as described has the following drawbacks:
(i) the small driving engagement area between the pins and the shoulders is not sufficient when significant torque is transmitted therethrough. For example, if a rider puts considerable force on the engagement due to riding up a steep hill, the pins may fracture due to over-stress, leading to failure of the freewheel sprocket and possible injury to the rider; and
(ii) the freewheel sprocket is often lubricated with oil but after a length of time, and especially in cold weather, the oil may in fact become thick and sticky whereby the pins do not release properly from their seats such that the engagement between the core and the collar is eliminated, leading to the bicycle becoming useless until the fault is determined and treated by a mechanic.
Thus, there is a long and unfulfilled need for a freewheel sprocket for a bicycle which provides reliable, even and secure engagement and release of drive input.
The object of the present invention is to provide a freewheel sprocket for a bicycle in which received torque is reliably and efficiently transmitted to a rear wheel hub on which the freewheel sprocket is mounted.
A further object of the present invention is to provide a freewheel sprocket in which engagement between a body and a sprocket wheel thereof is reliably actuated and released.
The freewheel sprocket of the present invention includes a flanged body, a sprocket wheel with a ratcheted bore and mounted over the body, a sleeve with a corrugated exterior and mounted between the body and the ratcheted bore of the sprocket wheel, a plurality of roller bearings received in the sleeve and evenly-dispersed between the body and the sprocket wheel, a first plurality of ball bearings and a second plurality ball bearings evenly dispersed on respective sides of the roller bearings, and a disk clampingly-retaining the ball and roller bearings in respective desired locations. The rollers move between a first position where they provide a driving mode between the sprocket wheel and the body, and a second position where there is a non-driving mode between the sprocket wheel and the body.
Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.